System and method for remediation of saline-alkali soil

Abstract

This invention belongs to the field of saline-alkali soil remediation, specifically relating to a remediation system and method for saline-alkali soil. The remediation system provided by this invention includes remediation columns and a mulch film. The remediation column comprises a columnar support mechanism and a continuously coated absorbent material. The columnar support mechanism is inserted into the saline-alkali soil to be remediated, with the lower end of the absorbent material contacting the saline-alkali soil to absorb brine. The mulch film is laid on the surface of the saline-alkali soil around the columnar support mechanism to inhibit moisture evaporation from the soil surface. Using this saline-alkali soil remediation system results in no wastewater discharge, and the system can operate continuously day and night without energy consumption, using minimal water and employing brine.

Description

Technical Field

[0001] This invention belongs to the field of saline-alkali soil remediation, specifically relating to a remediation system and method for saline-alkali soil. Background Technology

[0002] Saline-alkali soil is a general term for both saline and alkaline soils. Saline soil mainly refers to saline soils with high chloride or sulfate content; the soil is alkaline, but the pH value is not necessarily high. Alkaline soil refers to soils containing carbonates or diphosphates; the pH value is high, and the soil is alkaline. Saline-alkali soils have low organic matter content, low soil fertility, poor physicochemical properties, and contain more harmful anions and cations, making it difficult for crops to germinate. Soil salinization is a key abiotic factor interfering with food production, and the remediation of saline-alkali soils may help meet future food needs.

[0003] Currently, the main method for remediating saline-alkali soils is the water leaching method. Water is poured into the soil to form a water layer of a certain depth on the ground, which allows the salt in the soil to be fully dissolved. The dissolved salt is then drained away through drainage ditches, thereby reducing the salt content of the soil. This method is commonly used in saline-alkali areas with abundant water resources. It requires a large amount of fresh water to wash away excess salt in the crop root zone and will generate a large amount of saline wastewater. Summary of the Invention

[0004] This invention provides a system for the remediation of saline-alkali soil and its application in the remediation of saline-alkali soil, aiming to solve the problem of saline wastewater discharge in the remediation of saline-alkali soil.

[0005] To achieve the above-mentioned objectives, the first aspect of this invention provides a system for remediating saline-alkali soil, comprising:

[0006] The repair column includes a columnar support mechanism and a water-absorbing material continuously covering the surface of the columnar support mechanism. The columnar support mechanism is inserted into the saline-alkali soil to be repaired, and the lower end of the water-absorbing material contacts the saline-alkali soil to absorb the brine in the saline-alkali soil.

[0007] Mulch film is used to cover saline-alkali soil around columnar support structures to promote photothermal conversion and inhibit water evaporation from the saline-alkali soil surface.

[0008] The salinized soil remediation system of this invention includes a remediation column and a mulch film. After the salinized soil is irrigated with fresh water or low-concentration saline solution, the water-soluble salts in the salinized soil dissolve in the water. The resulting saline solution is inhibited by the mulch film and cannot evaporate from the surface, but is instead absorbed into the absorbent material and temporarily remains on the surface of the remediation column, thereby reducing the salt content in the salinized soil. The absorbent material continuously evaporates water and precipitates salts, thus continuously absorbing saline solution from the soil. Using this salinized soil remediation system results in no wastewater discharge, and the system can operate continuously day and night without energy consumption, using minimal water and employing saline solution.

[0009] In some embodiments of the present invention, the absorbent material is a fiber material or a gel material.

[0010] In some embodiments of the present invention, the mulch film is a hydrophobic mulch film; and / or, the light absorption efficiency of the mulch film is greater than 80%. Preferably, the mulch film is a black non-porous polyethylene film.

[0011] In some embodiments of the present invention, the salinized soil remediation system includes multiple remediation columns arranged in an array.

[0012] In some embodiments of the present invention, the columnar support mechanism is made of a corrosion-resistant material; and / or, the columnar support mechanism is one or more of a square tube, a triangular tube, a conical tube, and a circular tube; and / or, the tube wall of the columnar support mechanism has a hollow structure.

[0013] A second aspect of this invention provides a method for remediating saline-alkali soil, comprising the following steps:

[0014] Provide fresh water or seawater to the saline-alkali soils that need to be remediated;

[0015] Cover the saline-alkali soil to be remediated with plastic film;

[0016] Insert columnar support structures into the soil in the mulch film-covered area, cover the surface of the columnar support structures with continuous water-absorbing material, and ensure that the lower end of the water-absorbing material contacts the saline-alkali soil.

[0017] In some embodiments of the present invention, the method for remediating saline-alkali soil further includes: when the water-soluble salt content in the soil is less than 1 mg / g... -1 At that time, stop supplying fresh or seawater to the soil.

[0018] In some embodiments of the present invention, the method for remediating saline-alkali soil further includes: replacing the absorbent material with a new one when salt crystals appear on the top of the absorbent material, until the water-soluble salt content in the soil is less than 1 mg / g. -1 Stop supplying fresh or seawater to the saline-alkali soil to be remediated and replace it with new absorbent materials.

[0019] In some embodiments of the present invention, the method for remediating saline-alkali soil further includes, before providing fresh water or seawater to the saline-alkali soil to be remediated, placing the saline-alkali soil on an anti-seepage device.

[0020] In some embodiments of the present invention, the method for remediating saline-alkali soil further includes: blowing air onto the water-absorbing material to accelerate the evaporation of water. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 : A schematic diagram of the salinized soil remediation system provided by the present invention.

[0023] Figure 2 Evaporation rate during brine desalination process.

[0024] Figure 3 Temperature changes during the brine desalination process.

[0025] Figure 4 The positional selectivity of salt crystallization; wherein: (a) 5% saline solution; (b) 10% saline solution; (c) 15% saline solution; (d) 20% saline solution.

[0026] Figure 5 Evaporation rate of evaporation arrays ranging from 1×1 to 4×4.

[0027] Figure 6 : Condenser housing setup; where: (a) a photo of the condenser housing immediately after installation; (b) a photo of the condenser housing one hour after installation; (c) a photo of fresh water condensing on the surface of the condenser housing one hour after installation.

[0028] Figure 7 : A schematic diagram of the non-contact photothermal conversion utilization of the saline-alkali soil remediation system provided by the present invention.

[0029] Figure 8 The present invention provides a method for remediating saline-alkali soil, which is compared with traditional remediation methods. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0031] For simplicity, this document only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range. Similarly, any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, although not explicitly stated, every point or individual value between the endpoints of a range is included within that range. Therefore, each point or individual value can be used as its own lower or upper limit, combined with any other point or individual value, or combined with other lower or upper limits to form an unspecified range.

[0032] It should be noted that, in the description herein, unless otherwise stated, "above" and "below" include the stated number, and "multiple" in "one or more" means two or more. Relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0033] In the description of this specification, the references to terms such as "any embodiment / mode," "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0034] The above description of the invention is not intended to describe every disclosed embodiment or implementation of the invention. Exemplary embodiments are described in more detail below. These embodiments can be used in various combinations. In each example, the listing is merely representative and should not be construed as exhaustive.

[0035] The inventors discovered that although areas with saline-alkali soils generally lack freshwater, these areas are often accompanied by abundant saline resources, such as salt lakes, oceans, and groundwater. Therefore, based on the global distribution of saline-alkali land and its associated saline resources, utilizing saline water to remediate saline-alkali land is a more reasonable solution. However, directly irrigating soil with saline water increases the risk of soluble salt accumulation in the soil; therefore, the saline water must be converted into freshwater through desalination technology before irrigation. Traditional reverse osmosis and distillation desalination technologies face significant obstacles in agriculture due to their high energy consumption and high cost.

[0036] Solar interfacial evaporation is a low-energy, low-cost desalination method that converts solar energy into heat and fixes the heat at the evaporation interface to promote brine evaporation, thus achieving desalination from brine to freshwater. By eliminating dependence on traditional energy sources, using the freshwater generated by solar interfacial evaporation to leach saline-alkali land is a promising solution for the remediation of saline-alkali soils. However, traditional brine desalination and soil flushing methods inevitably generate large amounts of high-salinity wastewater. Coupled with inadequate local irrigation and drainage infrastructure, this high-salinity wastewater may exacerbate downstream land salinization. Therefore, researching methods for remediating saline-alkali land using brine that does not produce wastewater discharge is crucial.

[0037] Remediation system for saline-alkali soil

[0038] like Figure 1 As shown, the salinized soil remediation system provided by the present invention includes:

[0039] The repair column includes a columnar support mechanism and a water-absorbing material continuously covering the surface of the columnar support mechanism. The columnar support mechanism is inserted into the saline-alkali soil to be repaired, and the lower end of the water-absorbing material contacts the saline-alkali soil to absorb the brine in the saline-alkali soil.

[0040] Mulch film is used to cover saline-alkali soil around columnar support structures to promote photothermal conversion and inhibit water evaporation from the saline-alkali soil surface.

[0041] The salinized soil remediation system of the present invention includes a remediation column and a mulch film. The water-absorbing material on the surface of the remediation column can "extract" the brine in the soil to the surface of the adsorption column, so that the water evaporates from the surface of the remediation column and the salt remains in the water-absorbing material. The mulch film covering the soil surface around the remediation column can prevent the water from evaporating from the soil surface and keep the salt in the soil.

[0042] In some embodiments of the present invention, the absorbent material is a fibrous material or a gel material. The fibrous material is a composite material of one or more of cellulose fibers, alginate fibers, glass fibers, silica fibers, basalt fibers, and natural fibers, such as paper products, bamboo fiber products, carbon fiber products, bamboo charcoal fiber products, and cotton products. The gel material is one or more of biomass gel, polyacrylic acid gel, and PVA gel. In use, a thin layer of the gel material is coated on the surface of the columnar support structure, and after drying, it can absorb saline from the soil. In some embodiments of the present invention, the absorbent material is newspaper, filter paper, or toilet paper. The above absorbent materials can quickly absorb saline from the saline-alkali soil to be remediated, and the moisture easily evaporates from the surface of the absorbent material.

[0043] In some embodiments of the present invention, the mulch film is a hydrophobic mulch film; and / or, the light absorption efficiency of the mulch film is greater than 80%. Preferably, the mulch film is a black non-porous polyethylene film. The hydrophobic mulch film can effectively inhibit water evaporation from the ground surface. Simultaneously, the mulch film with a light absorption efficiency greater than 80% can convert sunlight into far-infrared light to drive the evaporation of brine moisture and salt crystallization in the absorbent material, thereby accelerating the remediation efficiency of saline-alkali soils.

[0044] In some embodiments of the present invention, the salinized soil remediation system includes multiple remediation columns arranged in an array, which can increase the evaporation area and thus accelerate the efficiency of salinized soil remediation. Preferably, the remediation columns are vertically inserted into the salinized soil to be remediated. Preferably, the mulch film does not contact the ground surface.

[0045] In some embodiments of the present invention, the columnar support mechanism is made of a corrosion-resistant material. Since the columnar support mechanism is in long-term contact with salt water, using a corrosion-resistant material can extend the service life of the saline-alkali soil remediation system. The corrosion-resistant material can be wood, bamboo, plastic, or wood-plastic composite materials.

[0046] There is no intention to restrict the shape of the columnar support mechanism. While ensuring its own strength, the cross-sectional shape of the columnar support mechanism can be one or more of the following: square cylinder, triangular cylinder, conical cylinder, and circular cylinder. The cylinder wall can be a perforated structure or a non-perforated structure; preferably, the cylinder wall is a perforated structure. The cylindrical structure of the columnar support mechanism facilitates airflow inside and outside the mechanism, and the perforated structure of the cylinder wall increases the contact area between the absorbent material and the air, accelerating moisture evaporation.

[0047] Methods for remediating saline-alkali soil

[0048] The method for remediating saline-alkali soil provided by this invention includes the following steps:

[0049] Provide fresh water or seawater to the saline-alkali soils that need to be remediated;

[0050] Cover the saline-alkali soil to be remediated with plastic film;

[0051] Insert columnar support structures into the soil of the mulch film-covered area, cover the surface of the columnar support structures with continuous water-absorbing material, ensuring that the lower end of the water-absorbing material contacts the saline-alkali soil, and then let it stand.

[0052] This invention allows for the direct remediation of saline-alkali soil using saline solution, as saline-alkali areas are often accompanied by groundwater salinization and possess abundant brackish water resources. However, reports indicate that long-term irrigation with saline solution carries the risk of exacerbating soil salinization. After irrigation, soluble salts in the soil dissolve in the water and crystallize after water evaporation. In traditional irrigation methods, water evaporates from the soil surface, leaving both the original soil salts and salts from the irrigation water in the topsoil, thus intensifying soil salinization. This invention employs an evaporation interface transfer strategy, laying a mulch film on the saline-alkali soil to be remediated to inhibit water evaporation from the surface and prevent salt precipitation from the soil. This ensures that irrigation water and soil salts are only absorbed into the remediation column along with the water and precipitate on the surface of the column, thereby enabling long-term saline-alkali irrigation of farmland. Figure 3 ).

[0053] In some embodiments of the present invention, the method for remediating saline-alkali soil further includes: when the water-soluble salt content in the soil is less than 1 mg / g... -1 At that time, stop supplying fresh or seawater to the soil.

[0054] In some embodiments of the present invention, the method for remediating saline-alkali soil further includes: replacing the absorbent material with a new one when salt crystals appear on the top of the absorbent material, until the water-soluble salt content in the soil is less than 1 mg / g. -1 Stop supplying fresh or seawater to the saline-alkali soil to be remediated and replace it with new absorbent materials.

[0055] In some embodiments of the present invention, the method for remediating saline-alkali soil further includes placing the saline-alkali soil on an anti-seepage device before providing fresh water or seawater to the saline-alkali soil to be remediated. In some embodiments, the anti-seepage device is a plastic film. Placing the saline-alkali soil on the anti-seepage device can prevent irrigation water loss and save water consumption.

[0056] In some embodiments of the present invention, the method for remediating saline-alkali soil further includes: blowing air onto the absorbent material to accelerate moisture evaporation. The absorbent material may also be heated or hot air blown onto it to accelerate moisture evaporation.

[0057] In actual use, there are 3,000 to 6,000 pillars per cubic meter of saline-alkali soil. The saline-alkali soil is irrigated at a water-to-soil volume ratio of approximately 1:1, and each cycle uses about 1 ton of water per cubic meter of saline-alkali soil.

[0058] Example

[0059] The following describes embodiments of the present invention. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0060] Unless otherwise specified, all soil samples were taken from Wuhan, Hubei Province. Sand, sub-clay, and clay were purchased from Chengjun Education Technology Co., Ltd. NaCl, CaCl2, NaHCO3, K2SO4, and Na2CO3 were purchased from China National Pharmaceutical Group Co., Ltd. The filter paper used for the absorbent materials was common rapid qualitative filter paper produced by Suzhou Baoweide Environmental Protection Technology Co., Ltd., the newspaper was commercially available waste newspaper, the toilet paper was produced by Jin Hongye Paper Group Co., Ltd., and the gauze was produced by Aomei Medical Co., Ltd. All aqueous solutions (resistivity = 18.2 mΩ / cm) were prepared with deionized water. The mulch film used was commercially available ordinary black PE mulch film. The columnar support structure used was a perforated plastic tube.

[0061] The method for determining the water-soluble salt content in soil in this invention:

[0062] Soil water-soluble salt content was determined according to NYT1121.16-2006. First, the soil was dried. The dried soil was ground into powder and added to pure water at a mass ratio of 1:5. After the salts in the soil were completely dissolved, the soil-water mixture was centrifuged and filtered to retain the soil extract. The soil extract was then dried, and the mass of soluble salts in the extract was recorded. In the final stage of drying the extract, hydrogen peroxide solution (purchased from China National Pharmaceutical Group Co., Ltd.) was added to completely oxidize the soluble organic matter in the extract. Finally, the soluble salt content was calculated according to the following formula:

[0063] c = m1·m3 / m2·m4 × 1000

[0064] Where c is the soluble salt content (mg·g) -1 m1 is the mass (g) of soluble salts in the extraction solution, m2 is the mass (g) of the extraction solution, m3 is the mass (g) of pure water, and m4 is the mass of soil.

[0065] Construction of a remediation system for saline-alkali soil:

[0066] First, cut the absorbent material into strips the same length as the column support structure and wide enough to wrap around the column support structure 1-5 times. Then, use adhesive to wrap the absorbent material around the surface of the column support structure, naming this structure a remediation column. Cover the soil with mulch film, and then insert the bottom of the remediation column into the mulch-covered soil.

[0067] Preparation of saline-alkali soil:

[0068] First, dry the soil and sieve it through a 20-mesh sieve. Then, mix the soil, pure water, and salts (NaCl, CaCl2, NaHCO3, K2SO4, and Na2CO3) in a 100:100:1 ratio until homogeneous. Finally, dry the soil and grind it.

[0069] The mass changes of the device were recorded using a balance (Mettler Toledo GmbH, ME204E, Switzerland). A xenon lamp (POPELECTRONICS GmbH, PLS-SXE 300, China) was used as a simulated solar light source, and its light intensity was calibrated to 1 kW·m using an optical power meter (POPELECTRONICS GmbH, PL-MW 2000, China). -2 The infrared imager (Hikvision Co., Ltd., H13, China) is used to record temperature changes and distribution during operation.

[0070] Example 1: Evaporation experiment under sunlight to determine the evaporation rate of brine desalination process

[0071] Experimental methods:

[0072] (1) Add 25g of fresh water to the beaker for the water evaporation experiment.

[0073] (2) Cover the freshwater with plastic film, then insert the bottom of the remediation column into the freshwater covered by the plastic film. Utilize a light intensity of 1 kW·m -2 The xenon lamp simulates sunlight and records the amount of evaporation, temperature changes, and temperature distribution during operation.

[0074] Experimental results: at 1kW·m -2 Under simulated sunlight, the device with a single repair column evaporated 2.51g of water within 2 hours. Figure 2 As shown, the evaporation rate can be divided into two stages: an acceleration phase within 1 hour and a steady-state phase after 1 hour. The evaporation rate reaches its maximum after 1 hour, reaching 38.63 kg·m³. -2 ·h -1 .

[0075] from Figure 3 As shown in the infrared images, the height of the water-wetted portion of the restoration column increases over time, during which the temperature of the restoration column remains significantly lower than the ambient temperature. This temperature difference allows the restoration column to harvest energy from the environment for water evaporation. This rapid evaporation, enhanced by ambient energy, can be maintained for at least 60 hours without significant change.

[0076] Example 2: Nighttime Moisture Evaporation Experiment

[0077] Experimental methods:

[0078] (1) Add 25g of fresh water to the beaker for the water evaporation experiment.

[0079] (2) Cover the freshwater with plastic film, and then insert the bottom of the remediation column into the freshwater covered with plastic film. Record the evaporation during the operation under dark conditions.

[0080] The results show that the evaporation rate under dark conditions can remain above 40% of that under illumination (the lowest measured rate was 41.9% under illumination), presumably because the temperature of the remediation column is consistently significantly lower than the ambient temperature. This temperature difference allows the remediation column to collect energy from the environment for water evaporation. Therefore, the salinization soil remediation system provided by this invention can operate in the dark, avoiding the limitation of traditional interfacial solar evaporators that cannot operate at night or on cloudy days.

[0081] Example 3: Desalination experiment with salt water of different salt concentrations

[0082] Experimental methods:

[0083] (1) Add 25g of salt water to the beaker for the desalination experiment.

[0084] (2) Cover the saline solution with a plastic film, then insert the bottom of the remediation column into the saline solution covered by the plastic film. Utilize a light intensity of 1 kW·m -2 The xenon lamp simulates sunlight and records the evaporation rate during operation.

[0085] like Figure 4 As shown, the crystallization of saline solutions with different salt concentrations on the surface of the repair column exhibits positional selectivity. This selectivity occurs because the saline solution continuously evaporates and concentrates as it is transported to the top of the repair column. High-concentration saline solutions reach saturation first and crystallize at the bottom of the repair column, while low-concentration saline solutions reach saturation later and crystallize at the top of the repair column.

[0086] The evaporation rate of the remediation column is unaffected by the saline concentration, and even slightly increases with increasing saline concentration. Firstly, this is due to the non-contact photothermal conversion mode. The mulch film used for photothermal conversion is not wetted by saline, and therefore no salt crystals form on its surface. Thus, unlike traditional interfacial evaporation devices, the saline-alkali soil remediation system provided by this invention is not affected by the reduced evaporation efficiency caused by salt accumulation on the surface of the photothermal material. Secondly, the salt crystallization on the surface of the remediation column increases the evaporation area, offsetting the reduction in evaporation rate caused by salt.

[0087] Example 4: Saltwater Desalination Experiment with Evaporation Arrays of Different Sizes

[0088] This embodiment uses 1×1 to 4×4 repair column arrays to measure evaporation rates to evaluate its potential for expanded application. Figure 5 As shown, the evaporation rate of a single repair column gradually decreases with increasing array size. This is because the repair columns in the array compete for environmental energy, and the array of repair columns suppresses vapor escape compared to a single repair column. However, the mass variation of the device gradually increases with increasing array size, as the number of repair columns in the array compensates for the competition among the repair columns.

[0089] In this embodiment, a 3×3 repair column array was used to measure the evaporation rate. The repair column array exhibited three phases of evaporation rate variation: the rising phase (0-50 min), the plateau phase (50-120 min), and the falling phase (120-240 min). This is because during the rising phase, the increased wicking height expands the effective evaporation area, increasing the evaporation rate to 16.25 kg·m³. - 2 h-1. When the wicking height stabilized, the evaporation rate of the repair column also reached a plateau. Finally, as the water that could be wicked into the repair column was depleted, the height of the water-wetted portion of the column gradually decreased, and the evaporation rate also gradually decreased. Despite the lower power density of natural light, the repair column exhibited a faster evaporation rate under natural light, reaching as high as 34.24 kg·m⁻¹. -2The evaporation rate h⁻¹ is much higher than the evaporation rate under simulated sunlight. This is likely because the wind in the outdoor experiment promoted the escape of vapor.

[0090] This embodiment further employs a 10×10 repair column array to investigate the interfacial evaporation performance of a larger-scale repair column array under natural light. Although the light power density is less than 0.5 kW·m². -2 However, the evaporation rate still reached 24.12 kg·m³. -2 ·h -1 .like Figure 6 As shown, this embodiment employs a 10×10 remediation column array with a condensation shell to further demonstrate the large-scale application potential of this columnar remediation system. When Yellow Sea seawater is added to the device and exposed to sunlight, freshwater with an ion concentration three orders of magnitude lower than seawater rapidly condenses on the shell surface. This freshwater can be used for drinking water or remediation of saline-alkali soils.

[0091] After irrigating saline-alkali soil with fresh water or low-concentration saline solution, the water-soluble salts in the soil dissolve in the water, and the resulting brine enters the absorbent material, thereby reducing the salt content in the soil. The absorbent material continuously evaporates water and precipitates salts, thus continuously absorbing brine from the soil. A mulch film laid around the columnar support structure on the surface of the saline-alkali soil plays an auxiliary role, effectively inhibiting water evaporation from the surface and promoting the absorption of brine into the absorbent material. This saline-alkali soil remediation system can remediate saline-alkali soil using a small amount of water and produces no high-salt leaching wastewater.

[0092] Example 5: Simulation Experiment of Freshwater and Saltwater Remediation of Saline-Alkali Land

[0093] 1. Experimental method for freshwater remediation of saline-alkali land:

[0094] (1) Mix 25g of saline-alkali soil and 25g of desalinated water in a beaker to make a water-soil mixture;

[0095] (2) Cover the soil-water mixture with plastic film, and then insert the bottom of the remediation column into the plastic film-covered soil-water mixture;

[0096] (3) Utilizing a light intensity of 1 kW·m -2 The xenon lamp simulates sunlight for desalination of water-soil mixtures; a cycle is completed when the evaporation rate drops to below 20% of its maximum value, and a cycle takes about 4 hours.

[0097] (4) After the previous cycle is completed, add 15g of desalinated water to the water-soil mixture in the beaker and start the next cycle;

[0098] (5) When the soluble salt content in the water-soil mixture drops to 1 mg·g -1 The following will not repeat.

[0099] 2. Experimental method for remediating saline-alkali land with saline solution:

[0100] (1) Mix 25g of saline-alkali soil and 25g of salt water in a beaker to make a water-soil mixture;

[0101] (2) Cover the soil-water mixture with plastic film, and then insert the bottom of the remediation column into the plastic film-covered soil-water mixture;

[0102] (3) Utilizing a light intensity of 1 kW·m -2 The xenon lamp simulates sunlight for desalination of water-soil mixtures; a cycle is completed when the evaporation rate drops to below 20% of its maximum value, and a cycle takes about 4 hours.

[0103] (4) After the previous cycle is completed, add 15g of salt water to the water-soil mixture in the beaker and start the next cycle;

[0104] (5) When the soluble salt content in the water-soil mixture drops to 1 mg·g -1 The following will not repeat.

[0105] When using freshwater to remediate saline-alkali land, the soil salinity increased from 11.04 mg·g⁻¹ within one cycle. -1 Decreased to 4.83 mg / g -1 56.25% of the soluble salts in the soil were removed. When saline solution is used to remediate saline-alkali land, soil salinity can still be significantly reduced, although the remediation performance decreases with increasing salinity in the water. Salts in the soil or irrigation water are transferred to the remediation column, forming regular crystals that adhere to the surface of the absorbent material. After remediation of saline-alkali land with high salt content, salts in the soil even formed visible crystals on the surface of the remediation column.

[0106] The results of the cyclic remediation experiment showed that after 5 cycles, the salinity of the saline-alkali land remediated with fresh water decreased from 11.04 mg·g⁻¹. -1 Reduced to 0.89 mg / g -1 The normal level was achieved after 7 cycles of treatment with 0.2% saline solution, reducing the salinity of the saline-alkali land from 11.04 mg / g. -1 Reduced to 0.95 mg / g -1 These results not only demonstrate the promising application potential of remediation columns in the remediation of saline-alkali soils, but also the feasibility of utilizing this invention for long-term irrigation with saline solution without the risk of soil salinization, providing more usable water sources for agricultural production in arid regions.

[0107] This embodiment also tested the effects of different soil types and salt types on the performance of the saline-alkali soil remediation system provided by this invention. It was found that, in addition to the salinity of irrigation water, the remediation performance of the saline-alkali soil remediation system provided by this invention is also affected by factors such as soil type and salt type. For sandy soils, loam, and clay, the remediation system exhibited the best remediation performance on sandy soils. Only one remediation session was needed to reduce the salinity of sandy soil from 11.04 mg / g. -1 Reduced to 0.38 mg / g -1 Reaching less than 1 mg / g -1 The desalination efficiency was 96.5% at the normal soil salinity level. The salt content of saline-alkali loam and clay soil decreased to 4.61 and 3.88 mg·g⁻¹, respectively. -1 The salt removal rate is approximately 60%. After one remediation session, the system can effectively reduce the salt content of saline-alkali soils caused by NaCl, CaCl2, NaHCO3, K2SO4, or Na2CO3 to 2.76-6.85 mg·g⁻¹. -1 .

[0108] Example 6: Field Trial

[0109] The field experiment was conducted in saline-alkali land in Jimo District, Qingdao, Shandong Province. First, a 10cm thick mulch film was laid on the bottom and sides of the soil in the experimental area to prevent salts from the bottom soil and soil outside the remediation area from seeping into the experimental area. The soil was then irrigated with water at a ratio of approximately 1:1 to saline-alkali soil. The mulch film was then covered on the soil surface. Finally, remediation columns were inserted into the soil. Water was replenished to the soil at 9:00 AM and 4:00 PM daily until the water-soluble salt content in the soil was below 1 mg / g. -1 .

[0110] Experimental Results: Due to seawater intrusion, the local soil had a high content of water-soluble salts, making it unsuitable for agricultural production. Only some salt-tolerant plants survived in certain areas. The soil desalination array operated stably both day and night. After 18 cycles, soil salinity decreased from 2.43% to 0.18%. Wheat seeds sown in the improved soil germinated (100%) and grew normally. Wheat planted on untreated saline-alkali land failed to germinate at all.

[0111] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A system for remediating saline-alkali soil, characterized in that, include: The repair column includes a columnar support mechanism and a water-absorbing material continuously covering the surface of the columnar support mechanism. The columnar support mechanism is inserted into the saline-alkali soil to be repaired, and the lower end of the water-absorbing material contacts the saline-alkali soil to absorb the brine in the saline-alkali soil. A mulch film is used to cover saline-alkali soil around a columnar support structure; the mulch film has a light absorption efficiency of more than 80% to convert sunlight into far-infrared light to drive the evaporation of brine moisture and salt crystallization in the absorbent material, and to inhibit the evaporation of moisture from the surface of the saline-alkali soil.

2. The soil remediation system for saline-alkali soil according to claim 1, characterized in that: The absorbent material is a fiber material or a gel material.

3. The soil remediation system for saline-alkali soil according to claim 2, characterized in that: The mulch film is a black, non-porous polyethylene film.

4. The soil remediation system for saline-alkali soil according to claim 1, characterized in that: The salinized soil remediation system comprises multiple remediation columns arranged in an array.

5. The soil remediation system for saline-alkali soil according to claim 1, characterized in that: The columnar support mechanism is made of corrosion-resistant material; and / or, The columnar support mechanism is one or more of the following: square tube, triangular tube, conical tube, and circular tube; and / or, The cylindrical wall of the columnar support mechanism has a hollow structure.

6. A method for remediating saline-alkali soil, characterized in that, Includes the following steps: Provide fresh water or seawater to the saline-alkali soils that need to be remediated; Cover the saline-alkali soil to be remediated with plastic film; Insert columnar support structures into the soil in the mulch film-covered area, cover the surface of the columnar support structures with continuous water-absorbing material, and ensure that the lower end of the water-absorbing material contacts the saline-alkali soil.

7. The method for remediating saline-alkali soil according to claim 6, characterized in that: The method for remediating saline-alkali soil also includes: When the water-soluble salt content in the soil is less than 1 mg·g -1 At that time, stop supplying fresh or seawater to the soil.

8. The method for remediating saline-alkali soil according to claim 6, characterized in that: The method for remediating saline-alkali soil also includes: When salt crystals appear on the top of the absorbent material, replace it with a new one until the water-soluble salt content in the soil is below 1 mg / g. -1 Stop supplying fresh or seawater to the saline-alkali soil to be remediated and replace it with new absorbent materials.

9. The method for remediating saline-alkali soil according to claim 6, characterized in that: The method for remediating saline-alkali soil further includes, before providing fresh water or seawater to the saline-alkali soil to be remediated, placing the saline-alkali soil on an impermeable device.

10. The method for remediating saline-alkali soil according to claim 6, characterized in that: The method for remediating saline-alkali soil also includes blowing air onto the absorbent material.

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